The antenna and antenna mounting assembly used on portable two-way radios are exposed to severe abuse and very high mechanical stresses. Users of two-way radios routinely use the antenna to pick-up the radio, such as when pulling the radio out of its carry case when it is being carried by the radio user.
A common method of making electrical connection between the radio electronics and the radio antenna requires electrically connecting an antenna nut or bushing, located on the radio housing to the radio electronics using a spring finger contact mounted on the radio printed circuit board which also makes contact to the antenna nut or bushing. In the second method, a coax cable is soldered between the radio printed circuit board and the antenna nut or bushing. The impedance of the connection from the radio printed circuit board to the antenna nut or busing is very critical to the electrical performance of the radio. Both the spring finger and coax connections used in the prior art antenna mounting approaches have drawbacks. The spring connection approach has the problem that the spring force and contact resistance can vary due to the tolerance stack-up associated between the antenna nut and the radio printed circuit board. The coax cable approach provides for improved electrical performance, but the labor time required for such an assembly increases the overall manufacturing cost of the radio.
Prior art antenna nut or bushings are commonly affixed to the radio housing in two ways. The first way is to insert-mold or ultrasonically swage the antenna nut or bushing into the radio housing which is typically manufactured using plastic. A common failure of insert molding or swaging the antenna nut is that the antenna nut is prone to break out of the plastic housing when subjected to high forces. Also, if the radio housing is highly stressed or deflected, the internal spring connecting the antenna nut to the radio electronics on the printed circuit board may become permanently damaged and loose electrical contact to the nut. The second method of affixing the antenna nut or bushing is to press fit the antenna nut or bushing into a metal casting. This method requires an additional insulating material between the antenna nut and the casting. Though stronger than insert molding or swaging, mechanical stress can also cause the press fit area to break. Press fitting the antenna nut can also cause high variance in the forces capable to be withstood between different radios. Some radios may exhibit stronger press fitted connections, while other radios may exhibit lower strength connections.
Thus, a need exists for an improved antenna mounting assembly and especially for an antenna mounting nut or bushing which can provide for a more reliable and stronger antenna connection.